Syringe driver/syringe/tube connecting set fluid delivery arrangement, and tube connecting sets therefor

ABSTRACT

A syringe infusion or other patient health care fluid delivery arrangement or system having a substantially constant force syringe holder/driver for a fluid-dispensing, preferably disposable, syringe to which an on-off valve and effectively bendably flexible tube connecting set are connected. The outside diameter of the tubing of an available flow-rate assortment of suitably identifiably marked tube connecting sets is formed of a desired single size by extrusion addition of a plastic outer overcoat layer over the inner fluid-carrying tubing, enabling interchangeable accommodation and securing thereon of standard single-size conventional or other desired connectors, whereby a single health care professional may fill a syringe with a prescribed dosage and concentration of health care fluid, and may also preselect and fix the delivery rate for the fluid, by selecting and assembling a given syringe holder/driver, fluid-filled syringe and tube connecting set. The syringe holder/driver is powered by a pair of Neg&#39;ator constant force springs which roll off and onto ball-bearing-mounted rotatable drums carried by a syringe plunger pusher or driver which is centered and guided in its longitudinal movement by the opposed Neg&#39;ator springs and the syringe plunger, which springs are laterally stabilized by nonsliding strip-laying stabilizing retentive engagement with, and strip-pickup removal from engagement with, the syringe holder/driver cover.

This invention relates to a syringe driver/syringe/tube connecting setfluid delivery arrangement, and tube-connecting sets for the continuoussteady-rate infusion of intravenous fluids or enteral nutrition fluidsto a patient, and for other health care fluid delivery requirements inmedical or other health care treatment procedures, and more particularlywhich enables the provision of ambulatory fluid infusion devices ofsimple construction which provide a high degree of reliability andsimplicity in utilization, as well as enabling the use of low-coststandard disposable syringe with a selected unique fixed flow rateself-metering tube connecting set coupled to a reusable compactnonelectrical substantially constant force-applying syringe holder andplunger driver.

In the prior art, one common practice has utilized gravity feed systemsin which the feed rate is adjusted by manual setting of adjustable pinchclamps on the connecting tube. Adjustable valves built into theconnecting tubes have also been used to selectively control the feedrate. Such systems generally have included a fluid container, a means ofgenerating a pressure differential between the fluid container and theinjection site, and a connecting tube between the fluid container andthe injection site. The flow rate of the manually adjusted valve sets isobserved by an in-line drip chamber where drops are counted manuallyover a measured time period. This system and method are prone to errordue to such factors as drop size variations with fluids having differentcharacteristics, including variations in surface tension.

Various electronic control systems have recently been provided,utilizing drop counters and microprocessor feedback systems whichelectronically regulate a flow control system.

In a further advance, accuracy was improved through use of a pistonchamber and piston, with precise mechanical reciprocation of the piston,in lieu of drop counting. This latter type of system is known as a pump,and delivers fluids under certain pump pressure. This type of systemposes a hazard in the event of occlusion. Various complicatingadditional mechanisms, such as pressure-sensing protectors or pressurerelief systems, have been utilized to alleviate or minimize this hazard.

In further prior art systems, syringes are used for continuous ratefluid delivery, utilizing electrochemical plunger driving systems inwhich the feed rate is adjustable as well as preset.

Ambulatory infusion is often desirable for patients who require precisecontinuous feed-rate medication delivery but are otherwise notbedridden. Various miniature battery-powered syringe pumps or smallbattery-powered piston or peristaltic pumps have been used for thispurpose. Versions of such arrangements have been implanted in the bodywhere long-term use is expected, with a subcutaneous port implanted toenable refilling of the drug reservoir.

In another type of ambulatory system, fluid feed pressure is achieved byuse of a rubber tube or bladder inflated with the fluid to be deliveredto the patient. In this system (such as shown in U.S. Pat. Nos.4,318,400, 3,895,631, 3,993,069, 4,140,117 and 4,201,207) the fluid flowrate is controlled by a short rigid glass capillary flow restrictorwhich is sized to provide the desired flow rate when the fluid is at aconstant predetermined pressure based on the theoretically predictableelasticity of the rubber forming the rubber tube or bladder. The shortlength of glass capillary is preceded in the fluid path by a filter toprevent particles in the fluid from plugging the very small orifice. Theflexible fluid-connecting tube is much larger than the orifice in theshort rigid glass capillary and essentially serves as simply a fluidconduit, the fluid flow metering through the connecting tube beingeffected by the short rigid capillary and accompanying filter, thelatter of which may vary in flow restriction as it filters out particlesand becomes more restrictive to flow therethrough. This entire device isused only one time and discarded.

In U.S. Pat. No. 4,298,000 to Thill, assigned to Minnesota Mining andManufacturing Co. (3M), a single constant-force spring, known andcommercially available under the trademark "Neg'ator," is utilized.Guidance for the spring is provided by a slide system. The constantspring force is applied to a syringe plunger to effect fluid pressure inthe system. However, as there is considerable friction in the reusableslide, as well as in the syringe plunger, the necessary spring force isquite high, and a mechanical toggle-type lever is used to apply thespring force after the syringe is in place. Because of the large forces,the device is inherently large, and is therefore unsuitable forambulatory infusion. The flow-rate in this system is fixed by theselection of a short plastic capillary tube inserted within the fluidpathway of a larger tube. In order to purge the air from the larger longconnecting tube, a two-position bypass valve is included which enablesthe user to switch from the slow controlled flow through the capillaryto the higher purge flow-rate bypassing the capillary. The smalldiameter of the capillary also requires the use of a filter upstreamfrom the capillary.

A similar syringe infusion device which is driven by a pair of Neg'atorsprings is disclosed in U.S. Pat. No. 4,381,006. In this patent, whichwas granted in 1983 and assigned to Abbott Laboratories, two Neg'atorsprings drive a syringe plunger, with relative sliding motion of theplunger and the motion-imparting element being guided by two slide rods.In this system the syringe constant fluid pressure system is coupled tothe injection site with a connecting tube which contains a variable flowrestrictor of the needle valve type.

In U.S. Pat. Nos. 4,557,728 and 4,447,232 to Sealfon, two Neg'atorsprings are employed to apply pressure to a collapsible bag. The springsdrive a box-like member which slides inside an outer box. No flowcontrol system is described for use in association with the device.

U.S. Pat. No. 3,670,926 to Hill discloses a slide guide system and asingle Neg'ator coil spring to compress a fluid bag. This arrangementwould not appear to provide constant pressure. There is reference to amanually operated pinch clamp to control flow.

In U.S. Pat. No. 3,647,117 to Hargest, a single Neg'ator constant forcespring compreses a bag to provide fluid delivery force. In an opticalarrangement, the coil spring appears to drive a syringe plunger. Itappears that there would be a problem in use of this arrangement due tothe frictional force of the rotating coil spring applying a lateralforce on the syringe plunger and causing binding or excessive friction.This device also uses sliding guide rails.

The extensive amount of prior patent art employing some means ofproviding a constant pressure fluid container (other than a gravity-fedbottle) coupled to some flow control system capable of very slowflow-rates is testimony to the long-felt need for a low-cost, compact,ambulatory intravenous drug administration system. The only devices ofwhich I am aware of having reached the market are the Thill device (U.S.Pat. No. 4,298,000 marketed by 3M) which is too large for ambulatorycare, and a device of the type shown by Peery et al and Buckles et alpatents (U.S. Pat. Nos. 4,318,400 and 3,895,631, respectively, marketedby Travenol) using inflated rubber fluid containers. To my knowledge,none of the others have formed a useful commercial product. The Thill(3M) device has had very limited marketing and, at one point, was takenoff the market. It has reentered the market in the last year, but hasstill not received much acceptance due to its size.

The Travenol inflated rubber container device is receiving muchacceptance in critical chemotherapy drug administration, where it isbeing sold as a "24-hour infusor" in which drug is delivered at the rateof 2 ml per hour. This product depends for flow-rate accuracy onconstant pressure developed by the inflated rubber tube or bladder.There are inherent problems with getting this pressure to be uniformfrom one device to the next. It appears that there are a great manyvariables in the production process of the rubber tube or bladder, aswell as elasticity changes due to age, heat, etc. The units are packagedin an expensive aluminum-foil-sealed pouch to protect from exposure tooxygen or light, both having deleterious effects on the rubber. Thelabeling of the units does not specify an accuracy tolerance. However,in prior art U.S. Pat. No. 3,993,069 (Column 3, Lines 12-16) it isstated that "If the pressure variation from the mean is more than tenpercent (10%), it is not possible to obtain the constant rates ofdelivery of liquid from the devices which are required by the presentinvention."

Another problem with the Travenol unit as marketed is the inability toeliminate all air bubbles after filling. While there is a description ofa method for removing the air in U.S. Pat. No. 4,318,400 (Column 4,lines 16-24), the air vent described in the patent and shown in theDrawings (64) does not exist in the device as now marketed. Instead,there is a note in the labeling that "The pea-sized bubble of air withinthe balloon reservoir is normal." However, in the view of the usercommunity, there is certainly a perceived, if not actual, hazard of airin intravenous delivery lines.

A further problem with the Travenol unit is the time required to filland inflate the rubber balloon container with the drug. It requires upto one minute to fill, due to the limited flow-rate through a 22- to20-gauge needle which enters the fluid cavity through a rubber septum.

Another important problem with the Travenol unit is the length of timeit takes to purge the air from the tube set, which is up to three (3)minutes. This is due to the short glass orifice flow restrictor builtinto the unit, followed by the flexible plastic tube set which is 36inches long and has a volume of approximately 0.1 ml.

Time is a valuable commodity for pharmacists, doctors and nurses who arepreparing these devices. The need for rapid purging of air is evidentfrom the above-described Thill (3M) device in which there is atwo-position valve provided, one position being for capillary tubebypass to enable rapid air purge, and the other position being fornormal flow through the capillary tube flow restriction section forfixed-rate flow control.

In all of the devices in the prior art in which very low flow-rates areprovided, either a single very small orifice flow-rate restrictor or aflow-rate restrictor having a multiplicity of minute pores isincorporated. Because of the very small openings in the flow-raterestrictor, there is a need for a filter upstream from the flowrestrictor to prevent particles from plugging up the flow restrictor.All medicaments are likely to contain microparticles. The single largeflow restrictor is less likely to encounter a particle large enough tototally stop flow. However, while the multiple pore-flow restrictorswill not normally plug completely as particles are lodged in the poreopenings during the course of the drug delivery, any particles notpassing through will cause an undesired and unpredictable reduction offlow rate. The single larger flow restrictor as used in the 3M andTravenol units is protected from plugging by having a filter upstream.This filter is, of course, also a flow restrictor, so any significantplugging of the filter will also reduce the flow-rate of the system.

All of the prior art devices have accomplished the flow-rate controlwith very expensive high precision flow restriction orifices and filterelements. They also must overcome the air purge problem with a bypassvalve arrangement, as in the Thill (3M) unit, or suffer with the slowair purge as in the case of Travenol unit.

Genese U.S. Pat. No. 4,381,006 (assigned to Abbott Laboratories)incorporates a pair of Neg'ator springs, as does the Sealfon U.S. Pat.No. 4,557,728 (assigned to Repro-Med Systems, Inc.) Both of thesedevices have slide members which serve as guides for the linear movementof the plunger. The use of the slide members in a reusable devicepresents a reliability problem in that, over a period of time, there isunpredictable friction in the system. As the friction force must besubtracted from the spring force to obtain the net force used to developthe constant pressure in the fluid, any change in the friction willchange the pressure and, thus, the flow rate. Any friction-bearingsystem employed over time will introduce a variable which can changeflow-rate and is certainly unpredictable.

In the case of the Abbot device (U.S. Pat. No. 4,381,006) a syringe isused which in itself has a friction force which can vary. This variablecan be managed since the variable can be predetermined to an acceptablelevel of confidence by statistical analysis of the measurement of thefriction forces in a large sample of the syringes to be used. However,the friction forces in the reusable spring-and-slide device can varysubstantially as the devices are used, due to dirt particles, fluids,corrosion, etc.

The Thill (3M) device uses a single reusable Neg'ator spring systemwhich necessarily has a guide system with variable friction. This isaccommodated by using a quite large spring force of a sufficiently largevalue that variations in the slide friction will be a small percentageof the total force applied. This Thill (3M) system thus requires moreforce be applied than a person can be expected to apply directly. Toaccommodate this requirement, the Thill (3M) device is made with a largelever arrangement to give a mechanical advantage in loading the syringeinto the spring force system. This is a large and heavy system whichrenders it substantially unusable for ambulatory care.

Cost, simplicity, ease of ambulatory portability and use, accuracy andreliability are all important factors in the acceptability and use of agiven infusion or other health care fluid delivery system and componentsand methods of manufacture and use thereof, and the prior art systemsand methods all suffer from one or more deficiencies in these and otheraspects.

It is an object of this invention to provide a low-cost, compact fluiddelivery system which enables the administration of fluids to a patientat a slow predetermined fixed rate which the patient cannot change, andwhich can be readily administered while the patient is ambulatory.

It is a further object of the invention to provide a fluid deliverysystem in which the contents of a fluid dispensing syringe, as well asthe flow rate therefrom, can be fixed by a pharmacist or other singlehealth care professional, whereby responsibility for correct drugadministration can be personally focused as to both drug concentrationand rate of delivery.

A further object of the invention is the provision of a more accuratehealth care fluid delivery system having less chance of variations inflow rate than that of prior art devices where flow is controlled by aconstant pressure device coupled to a flow restrictor.

It is also an object to provide a health care fluid delivery systemenabling a fixed preset substantially constant slow rate of fluiddelivery to a patient, yet which enables the relatively rapid purging ofair from the fluid path without the use of fluid bypass systems whichwould add cost and complexity as has occurred with various prior artsystems.

Another object of the invention is to provide a fluid delivery systememploying a simple substantially constant force syringe holder/driver,syringe and tube connecting set and in which essentially the onlymaterial mechanical movement friction losses are those resulting fromthe inherent friction encountered in sliding movement of a plunger inthe barrel of the syringe.

A further object of the invention is to provide a flexibletube-connecting set which serves the dual functions of effecting fluiddelivery through a bendably flexible path, and self-metering of fluidflow therethrough, while providing a maximum diameter flow pathway whichwill still provide necessary flow rate control.

It is also an object and feature to provide a substantiallyconstant-force-applying and substantially constant flow rate health carefluid delivery system enabling utilization of a low-pressurespring-loaded system, whereby any occlusion of the fluid administrationpath would not produce a hazardous condition.

Still a further object and feature of the invention is the provision ofdual function fluid delivery and self-metering fixed flow rate tubeconnecting sets.

Still other objects, features and attendant advantages will becomeapparent from a reading of the following detailed description of theinvention in its various aspects, taken in conjunction with theaccompanying drawings wherein:

FIG. 1 is an overall view, partially cut away for ease of illustration,of a syringe infusion arrangement according to the invention.

FIG. 2 is a section view taken on line 2--2 of FIG. 1.

FIG. 3 is a section view taken on line 3--3 of FIG. 2.

FIG. 4 illustrates an assortment of several interchangeablyinterconnectable tube-connecting sets constructed according to oneaspect of my invention.

FIGS. 5, 6 and 7 are enlarged section views taken respectively on lines5--5, 6--6 and 7--7 of FIG. 4.

FIGS. 8 and 9 are section views similar to FIGS. 5-7, showing modifiedtube-connecting set constructions employing respectively plastic andglass inner tubing according to one aspect of my invention.

FIG. 10 is a schematic illustration of the extrusion coating of sizedtubing according to one aspect of my invention.

Referring now in detail to the Figures of the drawing, a metered fluiddelivery syringe infusion assembly or arrangement 11 is provided, whichincludes a force-applying syringe holder/driver 13, to which a standardplastic syringe 71 may be suitably releasably secured for delivery of asuitable desired fluid to a patient infusion site PIS through aneffectively bendably flexible tube-connecting set 91, having a fluiddelivery needle 101 secured thereto as by a Luer-type connector 103,removably attached to a complementary Luer connector 99 on the end oftube connecting set 91. On-off flow control may be accomplished with asimple conventional on-off cut-off valve 81, which may be removablyconnected between the discharge end connector 79 formed on the fluiddischarge or exit end of the barrel 73 of syringe 71, and the Luerconnector 97 on the entrance end of the tube-connecting set 91.

Syringe holder/driver 13 includes a cover 21 which encloses a dualspring-driving assembly including a pair of oppositely outwardlyconvexly bowed Neg'ator constant-force coiled strip springs 51 which arewound about and are self-rolled onto and off of respective drums 45mounted in parallel-spaced relation on a longitudinally freely movableplunger/pusher or driver 41.

Springs 51 may be suitably self-secured onto the drums 45 as by multiplewraps thereabout, or may be otherwise suitably secured thereto at theirends if so desired. At their respective opposite ends 51a, springs 51may be suitably crimped and secured about respective anchor pins 39press-fit into upstanding parallel anchor shoulders 37 on ananchor/securing block 31, between which anchor shoulders 37 the springs51 extend in substantially laterally centered relation, front-to-back asviewed in FIG. 1.

Drums 45 are each mounted on ball bearings 45a to minimize frictionalresistance to rolling and unrolling of the springs 51 onto and fromtheir respective drums 45, each of the bearings 45a being in turnmounted on a respective one of two spaced parallel axle or support pins47 which are press-fit into upstanding parallel-spaced drum supportshoulders 44 extending in close relation on either side of the drums 45,from a transverse pusher or driver seat 43.

Anchor/securing block 31 has a central circular mouth 33 formed therein,which accepts and accommodates the entrance and exit of plunger 77therethrough for syringe-loading of the holder/driver 13.

Pusher or driver seat 43 has an annular peripheral lip 43a whichcomplements flanged end 77a of plunger 77 and centers and aligns theplunger pusher or driver 41 with the finger-gripping flanged end 77a ofsyringe plunger 77, which plunger 77 and syringe barrel 73 is in turnsubstantially centered relative to mouth 33 of the anchor/securing block31.

Anchor/securing block 31 also has formed on its lower (as viewed inFIG. 1) exterior face a front-to-rear transverse end face slot 35connecting with the circular mouth 33 and which has a transverse slotwidth sufficient to accommodate the transverse distance between opposedparallel flaconventional finger-grip flange 75 of syringe barrel 73, theend face slot 35 being of lesser width than the oppositely extendingradially extended round flange lip portions 75fl of the flange 75.Transversely concave grooves 35g are formed in the opposite parallelside walls 35w of end face slot 35 of a size to complementarily receiveand retain opposed radially extended round flange lip portions 75fl whenthe syringe barrel flange 75 is inserted into slot 35 and rotated 90°.Groove 35g and associated retention lips 35a forming a lower wall ofgroove 35g thus retain the lip portions 75fl of barrel flange 75 in thus90° rotated position of the syringe barrel 73 and thereby hold thedistended syringe 71 centrally of and with its plunger 75 extendingwithin central mouth 33 of the syringe holder/driver 13.

In the quiescent state of syringe holder/driver 13 prior to loading asyringe therein, the springs 51 are rolled into retracted woundcondition onto their respective drums 45, and the plunger/pusher ordriver 41 is thereby pulled down and resiliently held by springs 51 incentrally seated position against the top edge surfaces ofanchor/securing block shoulders 37, as shown in phantom lines in FIG. 1.In this position, the springs 51 bow outwardly and engage the adjacentopposite inner walls of cover 21 over a relatively short extent.

The syringe 71 as shown in fluid-filled and assembled loaded conditionin FIG. 1 is loaded into the holder/driver 13 after first filling thesyringe with a desired quantity of a fluid IF desired to be administeredto a patient, and closing the valve 81 to "off" position to preventescape of fluid from the syringe 71 during loading of the syringe 71into holder/driver 13 and prior to desired fluid expulsion from thesyringe 71.

The syringe plunger 77 will be extended to the extent of its partial orfully filled condition, and the thus-extended plunger is insertedthrough mouth 33 into centered engagement with the plunger/pusher ordriver 41. Syringe barrel 73 is pushed upwardly to thereby push plunger77 and plunger/pusher or driver 41 upwardly away from anchor/securingblock 31, until the finger grip flange 75 of syringe barrel 73 seatsagainst the recessed flat base of end face slot 35 in anchor/securingblock 31, with the opposing parallel flats 75ff of flange 75 parallel tothe side walls 35w of end face slot 35. Thereupon, the barrel 73 isrotated 90° to engage the flange lips 75fl in the complementary concavegrooves 35g.

In this loaded assembly of syringe 71 with syringe holder/driver 13, theplunger/pusher or driver 41 will be held away from the anchor/securingblock 31 by the extended syringe plunger 77, and the oppositelyoutwardly bowed Neg'ator constant force strip springs 51 will beextended from their rolled-up position and will lay generally againstthe respective opposite inner sidewalls of cover 21 as indicated at 51a,although extended distention of spring 51 may pull the spring sufficienttaut to cause the substantial extent of spring length 51a to be spacedinwardly away from the adjacent wall of cover 21. The thus extendedsprings exert the desired constant expulsion or driving force on plunger77 to effect fluid discharge through the effectively bendably flexibletube-connecting set 91 and needle 101 for expiration and subsequentpreset metered delivery of fluid IF to a patient.

In the plunger-driving movement of the plunger/pusher or driver 41 bysprings 51, it will be seen that the plunger/pusher or driver 41 is freeof sliding engagement with the cover 21 or any other part, and thesprings 51 roll up onto the negligibly low friction ball bearing mounteddrums 45, while simply moving in successive incremental strip-pickupfashion away from the opposite stabilizing and protective walls of cover21, without any sliding contact therewith. Thus, essentially the onlymaterial mechanical friction force acting in the fluid delivery actionof the holder/driver 13/syringe 71 assembly is that inherent in thesliding contact discharge movement of plunger 77 along syringe barrel73. It will be appreciated, of course, that this statement is notintended to refer to absence of fluid flow resistance through the tubeconnecting set, as such fluid flow resistance on a precisionpredetermined basis is an important feature of one aspect of theinvention.

The syringe 71 may desirably be a standard disposable syringe, thebarrel 73 of which may be molded of polypropylene or other suitableplastic material, the molded plastic plunger 77 having a conventionalmolded rubber end seal which fits snugly in sliding contact within thebarrel 73. The plunger 77 is moved longitudinally within the barrel 73to either aspirate or to inject a fluid solution IF, after filling withfluid IF through the rear of barrel 73. It will be appreciated that afriction force is produced between the wall of barrel 73 and the endseal on plunger 77 by this plunger movement, which friction varies withthe size of the syringe.

It is desirable to employ a fluid pressure within the syringe 71 whichis not in excess of 650 mmHg, or 12.6 psi. Pressures greater than thiscould be hazardous if an occlusion should occur in the fluid flow path.In the practice of the present invention, I have found it feasible tomaintain a fluid delivery system pressure within a relatively close andacceptable tolerance of a safe 11.5 psi, and to enable provision ofsyringe fluid delivery arrangements 11 which can be constructed andsized to enable use of all syringe sizes from 3 ml to 60 ml whileattaining this fluid delivery system pressure objective. The plungerarea of a standard 3 ml syringe is 0.096 square inch, while the area ofthe standard 60 ml syringe plunger is 0.858 square inch. Accordingly,the force to develop 11.5 psi in the 60 ml syringe is 9.867 pounds, andthe force required for the 3 ml syringe is 1.104 pounds.

Standard disposable syringes in the 60 ml size have friction varyingfrom 1.18 pounds to 2.043 pounds, while the 3 ml syringe varies infriction from 0.118 pounds to 0.306 pounds. These syringe forces must besubtracted from the essentially constant-plunger-driving force providedby springs 51 acting through pusher or driver 41, to obtain the netforce available to develop the objective 11.5 psi for the fluiddelivering system. Table I shows the syringe friction force averages, aswell as the minimum and maximum forces and pressures encountered, basedon analysis of the range of friction forces for the various standardsyringe sizes from 3 ml to 60 ml, which friction forces can be predictedto an acceptable degree of variation.

                                      TABLE 1                                     __________________________________________________________________________          Total                                                                         Spring                                                                            Avg.                                                                             Avg.                                                                              Min.                                                                             Max.                                                                              Max.                                                                             Min.                                               In.sup.2                                                                         Vol                                                                              Force                                                                             Fric-                                                                            Net Fric-                                                                            Net Fric-                                                                            Net Avg.                                                                             Max Min Max                                                                              Min                              Area                                                                             ml (lb)                                                                              tion                                                                             Force                                                                             tion                                                                             Force                                                                             tion                                                                             Force                                                                             psi                                                                              psi psi Δ%                                                                         Δ%                         __________________________________________________________________________    0.858                                                                            60 11.567                                                                            1.700                                                                            9.867                                                                             1.180                                                                            10.387                                                                            2.043                                                                            9.524                                                                             11.5                                                                             12.106                                                                            11.100                                                                            +5.3                                                                             -3.5                             0.691                                                                            35 8.320                                                                             0.373                                                                            7.947                                                                             0.313                                                                            8.007                                                                             0.431                                                                            7.889                                                                             11.5                                                                             11.588                                                                            11.417                                                                            +0.8                                                                             -0.7                             0.500                                                                            20 6.145                                                                             0.395                                                                            5.750                                                                             0.312                                                                            5.833                                                                             0.490                                                                            5.655                                                                             11.5                                                                             11.666                                                                            11.310                                                                            +1.44                                                                            -1.7                             0.304                                                                            12 3.937                                                                             0.441                                                                            3.496                                                                             0.271                                                                            3.666                                                                             0.584                                                                            3.353                                                                             11.5                                                                             12.059                                                                            11.030                                                                            +4.9                                                                             -4.1                             0.096                                                                            3  1.309                                                                             0.205                                                                            1.104                                                                             0.118                                                                            1.191                                                                             0.306                                                                            1.003                                                                             11.5                                                                             12.406                                                                            10.448                                                                            +7.9                                                                             -9.1                             __________________________________________________________________________

It will be appreciated that the syringe 71 and syringe holder/driver 13arrangement according to the present invention, and as shownillustratively in FIG. 1, enable the employment of low forces andpressures where the friction range of the syringe plunger 77 is small inrelationship to the force used to achieve the pressure. If more frictionvariation were introduced into the system by the use of any slidingguide system for the syringe holder/driver 13, as has been present withvarious prior art systems, it would be necessary to use high forces andpressure to stay within the ±10 percent variation limit, which wouldintroduce a hazardous condition in the event of occlusion of the fluidpath, as well as creating a materially larger mechanical syringe driverarrangement which would be both heavier and require more syringe-loadingforce, and also rendering the arrangement nonambulatory, as is the casewith the previously discussed 3M unit.

The tube connecting set 91 has conventional Luer connectors 97, 99secured onto opposite ends of flexible tube 93, and is removably lockedin fluid delivery connection with the syringe 71 by conventionallyremovably locked engagement with a complementary connector 83 onintermediate connecting on-off cut-off valve 81 in the illustrativeexample.

Tube connecting set 91 serves the dual function of providing aneffectively bendably flexible fluid conduit for suitable manipulationand connection to a patient infusion site PIS or other patient fluiddelivery site, as well as serving as a preselectable predetermined fixedmetered flow rate control means for precise preset controlled deliveryof fluid IF to a patient. To this end, the tube 93 is constructed to beeffectively bendably flexible and its inside flow path diameter alongits entire length is essentially uniform, being sized in both ID andlength to accomplish the necessary flow restriction for the givenpressure so as to achieve the desired flow rate. As used herein, theterm "effectively bendably flexible" is employed to refer to thepractically necessary flexibility required for conventional health careuse in connecting a separate syringe, such as employed in the presentinvention, to a patient delivery site such as a patient infusion sitePIS, and it has been found in practice that such necessitates theability to bend through an arc of as small as approximately three-inchradius without taking a set. This may be acceptably accomplishedaccording to this invention, as will be described further along.

According to one practical example, the tube connecting sets 91 arenominally 36 inches in length; however, variations of six inches eitherway are acceptable and usable under health care practice. Flow rateswhich are conventionally desired may range from 0.1 ml per hour to asmuch as 100 ml per hour.

Since there is a necessary variation in pressure due to the frictionvariations of the syringes 71, it is critical that the flow restrictionprovided by the tube connecting sets 91 be very accurate if the totaltolerance for flow delivery rate to a patient is to be maintained within±10 percent.

The inside diameter ID of a 36-inch-long tube having a flow rate 0.1ml/hour, with a pressure drop of 11.5 psi, is theoreticallyapproximately 80.39 uM. Calculation of this approximate ID is based onthe well-known Poiseuille's Law, expressed in simplified form by theequation: ##EQU1## where Q is the flow rate in ml/sec, P is the pressuredrop in the tube in dynes per square cm, r is the internal radius in cm,l is the length of the tube in cm, and n is the liquid viscosity inpoise, and in which the fluid flow is assumed to be laminar and steadythrough a length of straight circular tubing of constant diameter. Inthe above calculation of flow rate, the liquid is assumed to be water at20° C., with a viscosity of 0.01005 poise. It will be appreciated that,in actual practice, the health care fluid to be administered willusually be more viscous, producing a flow rate of the order of about tenpercent slower, thus requiring appropriate adjustment of insidediameters employed for various fluids IF being employed, and suchconversion may be readily accomplished. For purposes of simplicity ofdiscussion herein, the calculations assume that the fluid IF is water.

With the variations in inside diameter affecting the flow rate by thefourth power of inside diameter dimension variations, it can be readilyrecognized that the requirement for a tube connecting set 91 with thisdesign, which is very precise is not practical as an ordinary matter,considering that commercially available tubing made of acceptablematerials such as plastic, stainless steel or glass (fused silica) has atolerance, as commercially supplied, of ±3 uM in the size required for0.1 ml/hour flow rate, and ±6 uM in the size for 0.2 ml/hour flow rate.This would result in variations of ±15 percent in flow rate, which wouldresult in a total system flow rate variation of up to 25 percent whencoupled with the variation caused by the syringe piston friction. Thiswould be totally unacceptable for the intended use of drug fluidsadministration.

A unique method of achieving very close tolerance flow control in thetube connecting sets is provided, according to one aspect of myinvention. By measuring commercially available tubing with commercialtolerances, it has been found that a coil of the tubing produced in asingle continuous run is very uniform in dimension throughout the fulllength of the coil, the end-to-end variation for a 10,000-foot length ofstainless steel tubing being normally within three or four percent orless, for plastic tubing within eight or nine percent, and for glasstubing within approximately four or five percent. In the illustrativeexample of 36-inch nominal length tube 93, samples of a production coilof tubing are taken from both ends of the coil and tested for flow rateusing 36-inch-long samples, the test average being taken as the36-inch-length flow rate.

The variation in flow rate produced by length variation is indirectlyproportionate to length according to Poiseuille's Law. If a tested tubeat 36-inch length is found to have a flow rate which is ten percent toohigh, this entire coil is marked to be cut to a length which is tenpercent longer, or 39.6 inches. This longer length reduces the flow byten percent, to thereby effect the desired flow rate through this lengthof the particular run of tubing.

Referring to FIG. 10, after the tubing 93a (designated in FIG. 10 as693a) of a particular production run coil 621 has been tested, theentire coil 621 of tubing 693a, which may suitably be on a supply spoolor reel 611, is run through an extruder 631 which adds an overcoat orlayer of plastic 693b over the original tubing 693a, thereby forming acomposite tubing 693 of enlarged outside diameter of, for example,approximately 1/16-inch OD, which is uniform along its length and whichuniform enlarged outer diameter is interchangeably employed for all coilID sizes, thereby enabling the provision of an interchangeably uniformOD, e.g. approximately 1/16 inch, for all tube connecting sets 91, whichalso enables accommodation and use of standard uniform single sizeconnectors such as Luer-type connectors 97, 99. The plastic extrusionovercoated tubing 693 may subsequently be cured as by passing theovercoated tubing 693 through a suitable curing device 671, after whichthe cured composite overcoated tubing 693 may be taken up into a take-upreel or spool 681 for subsequent cutting into lengths. This pretestedand overcoated tubing is then cut to the specified length for theparticular desired flow rate, to obtain tubing lengths which will haveprecisely the correct flow rate at the desired 11.5 psi pressure.Fittings are affixed to each end, which are standard Luer-typeconnectors, by use of adhesive, heat or insert plastic molding.

The extruded plastic layer 693b may be distinctively colored, or otherindicia my be applied, to indicate the designated flow rate. Sincelength variations of the tube connecting sets 91 of up to 17 percent or±6 inches are acceptable in actual use, this method of achieving preciseflow rates allows the production of very low-cost metering tubeconnecting sets 91.

The further advantage of having a tube connecting set in which theentire length is of uniform interior dimension is that there is no needfor a method for fast air purging of the line as is the case with priorart devices. The total volume in the tube 93 is so low that the fluidfills the tube in about 20 seconds for the 2.0 ml/hour set, as comparedwith three minutes for the prior art Travenol unit at the same flowrate. In the Travenol unit there is no bypass to purge the air, and theperson doing the filling must wait for the three-minute purge beforeclosing off the end of the tube.

In the practice of this invention there may be situations where tubeconnecting sets of other nominal lengths are desired. In this situation,flow control tube connecting sets of shorter or longer nominal lengthcould be prepared, using the same method and construction. Also, ametering flow control tube connecting set according to this inventionmay, if desired, be used in conjunction, such as in tandem or series,with another conventional tube connecting set, such as a tube connectingset of substantially larger effectively nonmetering interior diameter.

By using longer lengths of tube with larger ID's as flow restrictors,the need for a filter upstream in the fluid path to prevent occlusion islargely alleviated, since the long tubing lengths permit using muchlarger interior diameters for flow restriction. The resultant largerdiameter, which may be thus employed while still effecting the desiredflow restriction and fixed metered flow rate, is much greater than anylikely particle in a medical fluid, and thus need not be protected by anupstream filter. Such a filter in prior art devices is an additionalsource of variation in flow rate since the pressure drop through afilter may vary due to variables in the manufacture or placement of thefilter. The uses of a filter also means that, as the fluid isadministered, there is a likely build-up of particles on or in thefilter which will cause an increasing pressure drop during the fluidadministration which would result in a reduced flow rate as the fluid isgiven.

For comparison, the Travenol infusor uses a rigid very short capillary(i.e. 4 mm length) with 490 mmHg pressure (9.478 psi). This calculatesto require a 45.7 uM (0.0018-inch) inside diameter. The presentinvention, on the other hand, enables use of a substantially larger IDdual function effectively bendably flexible precision self-metering longtube connecting set 91 of, for example, as much as 42 inches or more inlength, and which may also, if desired, be of shorter nominal or actuallength such as, for example, three inches, for acceptable flow rateswith commercially available effectively flexible bendable tubing havinginterior diameters which enable metered flow-controlled fluid deliverywithout necessity for an upstream filter.

Since the inside diameter changes proportionately to the fourth power ofthe reciprocal of the length according to Poiseulle's Law, there is avery large increase in the tube diameter when going from a short rigidcapillary length, as employed in the Travenol infusor, to the lengthsemployed for practical effectively bendably flexible tube connectingsets 91 as afforded in practice of the present invention. For a typical2 ml/hour flow rate, the following are the theoretical inside diametersand lengths for effectively bendably flexible tube connecting sets 91according to this invention, using 11.5 psi fluid pressure (water fluidIF).

    ______________________________________                                        Length       Inside Diameter                                                  (inches)     (Microns = uM)                                                   ______________________________________                                        36           170.0                                                            42           176.7                                                            18           143.0                                                            9            120.2                                                            6            108.6                                                            3            91.3                                                             ______________________________________                                    

For purposes of practice of the invention to achieve the desiredeffectively flexibly bendable tubing 93 of the tube connecting sets 91,this may be attained with any one of stainless steel, glass or plasticinner tubing 93a (the hundreds prefix numbers 1-6 being added to theoriginal reference numeral 93a (e.g. 193a, 293a, etc.) for the innertubing simply to designate various illustrative forms or physicalembodiments of the tubing 93a, as well as the overcoat layer 93b (e.g.193b, 293b, etc.), composite tubing 91 (e.g. 191, 291, etc.). Thepreferred material for the inner tubing 93a is stainless steel, dueparticularly to the smaller coil end-to-end ID tolerance variationsfound in production coil runs thereof, although the conventionalproduction runs of plastic tubing and glass tubing are acceptable. Toassure that the composite tubing 93 is effectively bendably flexible,the OD of the inner tubing 93a should be no greater than approximately 2mm, and the wall thickness thereof no greater than approximately 0.5 mm,larger sizes being too stiff for conventionally necessary or desirablypractical bending application of the tube connecting sets 91 as IVfeeding connecting tubes, which is a conventional use for the tubeconnecting sets 91. The inner tubing sizes employed in the illustrativeexamples herein for the range of various practically encountered flowrate requirements and syringe sizes being of the order of 0.5 mm OD orless and 0.1 mm wall thickness or less, ample effectively bendableflexibility for the tube connecting sets 91 is provided.

Illustrative examples of variations in flow rate attainable by ±6-inchvariations from a 36-inch nominal length of various different nominal IDtubing are shown in the following Table II, together with maximum andminimum ID tolerance variations which would result in necessity for±6-inch tube length variations to accommodate these maximum and minimumID variations. This Table II also indicates the maximum and minimumcommercial tolerance variations of tubing ID for the respective nominalID sizes, illustrating that normal commercial tolerance variations intubing ID will not require greater than ±6-inch length variations.

                                      TABLE II                                    __________________________________________________________________________                                             Max/Min                                                                 Max/Min                                                                             Commercial                           Seconds  36" Length                Tolerance                                                                           Tolerance                                to   Nominal                                                                            ID     30" Length                                                                          42" Length                                                                            ΔID (uM)                                                                      ΔID (uM)                       Flow &                                                                            flow ID   Vol.   ID  Δ                                                                          ID  Δ                                                                          for ± 6"                                                                         from                                 ml/hr                                                                             36"  uM   cm.sup.3 × 10.sup.-4                                                           uM  %  uM  %  ΔL                                                                            Nominal                              __________________________________________________________________________    0.1 167.0                                                                              80.39                                                                              46.4   76.81                                                                             4.46                                                                             83.55                                                                             3.93                                                                             +3.2  ±3                                                                   -3.6                                       1.0 52.8 142.96                                                                             146.8  136.59                                                                            4.46                                                                             148.57                                                                            3.93                                                                             +5.61 ±6                                                                   -6.37                                      1.25                                                                              47.3 151.16                                                                             164.1  144.42                                                                            4.46                                                                             157.10                                                                            3.93                                                                             +5.94 ±6                                                                   -6.74                                      2.0 37.4 170.00                                                                             207.55 162.42                                                                            4.46                                                                             176.68                                                                            3.93                                                                             +6.68 ±6                                                                   - 7.58                                     5.0 23.6 213.77                                                                             328.2  204.24                                                                            4.46                                                                             222.17                                                                            3.93                                                                             +8.40 ±12                                                                  -9.53                                      10.0                                                                              16.7 254.22                                                                             464.1  242.89                                                                            4.46                                                                             264.21                                                                            3.93                                                                             +9.99 ±12                                                                  -11.33                                     20.0                                                                              11.8 302.23                                                                             656.0  288.76                                                                            4.46                                                                             314.10                                                                            3.93                                                                             +11.87                                                                              ±12                                                                  -13.47                                     30.0                                                                              9.6  334.57                                                                             803.9  319.66                                                                            4.46                                                                             347.71                                                                            3.93                                                                             +13.14                                                                              ±12                                                                  -14.91                                     60.0                                                                              6.8  397.87                                                                             1136.9 380.14                                                                            4.46                                                                             413.50                                                                            3.93                                                                             +15.63                                                                              ±12                                                                  -17.73                                     90.0                                                                              5.6  440.32                                                                             1390.4 420.70                                                                            4.46                                                                             457.62                                                                            3.93                                                                             +17.30                                                                              ±12                                                                  -19.62                                     __________________________________________________________________________

According to the invention, an assortment of tube connecting sets 191,291, 391 may be made and supplied for use by a health care professional,the assortment including assorted different ID and flow rate connectingsets 191, 291, 391 (see FIG. 4 and enlarged cross section views in FIGS.5-7) all of which have a tubing 193 outer diameter, e.g. 1/16-inch,formed by a respective plastic outer overcoat layer 193b, 293b, 393b andall of which have interchangeably usable Luer connectors 97, 99 on theiropposite ends. Each different flow rate size tube connecting set, withits respectively appropriately-sized inner tube ID and cut tubinglength, may be suitably indicated by color or other indicia in and/or onthe respective tubing overcoat layer 193b, 293b, 393b thereby providingdistinctive indicia in association therewith to enable a health careprofessional to determine its respective flow rate rating. A singleresponsible health care professional, such as a pharmacist, may thusfill the syringe 71 with the prescribed dosage and concentration of theprescribed health care fluid to be administered to a patient and, basedon this information and his own knowledge and/or the prescribingphysician's order, he will thereupon select the appropriate flow ratetube connecting set from the assortment of interchangeably fittabledifferently metered tube connecting sets 191, 291, 391, etc., it beingappreciated that additional selections of tube connecting sets greaterthan the illustrative three sets of the illustrative small assortment ofFIG. 4 are desirably provided in order to enable the pharmacist toselect and preset the precise flowrate required for a given need andfluid delivery assembly 101.

The tube connecting set selected from the assortment is then connectedto the syringe 71 and cut-off valve 81, thereby providing a properlyfilled syringe 171 and preset metered flow rate tube connecting set foruse as by a nurse or other suitably qualified health care personnel,after suitable expiration, to administer the fluid to a patient simplyby inserting and securing the needle 11 to a patient and opening thevalve 81, thereby minimizing the likelihood of inadvertent mistakes indosage, concentration, content or rate of delivery of the prescribedhealth care fluid to a patient. The filled syringe 71, with cut-offvalve 81 in closed position, may be loaded into syringe holder/driver 13either prior to or after attachment of the selected tube connecting set91 to the cut-off valve 81.

FIGS. 8 and 9 illustrate plastic-overcoated tubing 493 and 593 for tubeconnecting sets according to the invention, having respectively plasticand glass inner fluid-path-forming tubing 493a and 593a, the respectiveouter plastic overcoat layers 493b and 593b being of a single commondiameter, as previously described for the previously describedembodiments.

While the invention has been described with respect to variousillustrative embodiments, it will be apparent to one skilled in the artthat various modifications and improvements may be made withoutdeparting from the scope and spirit of the invention. Accordingly, theinvention is not to be limited by the illustrative embodiments, but onlyby the scope of the appended claims.

I claim:
 1. A kit arrangement for delivering a fixed predetermined rate of flow of a selected fluid to a patient comprising:a syringe having a body with a fluid discharge opening therein and a plunger slidable in said body to discharge fluid through said discharge opening, constant force driver means connectable to said syringe for exerting a constant discharge-effecting relative motion between said syringe plunger and said syringe body, and an assortment of tube connecting sets for selective connection of said syringe body discharge opening to a patient for delivery of fluid thereto from said syringe body, each of which tube connecting sets has the additional dual function of forming a fixed flow rate fluid metering means, each of said tube connecting sets of said assortment being formed of a flexible tubing section having a bore of substantially constant cross section size along its length and being substantially larger in cross-section than any particle which might occur in a medical fluid to be delivered therethrough, so as to enable said tubing section to form a predetermined fixed flow rate fluid metering means which is fully operational without need for a filter, said assortment of tube connecting sets including a plurality of tube connecting sets each of which itself forms a combined flexible tube connecting set and predetermined fixed flow rate metering means and provides a different one of a plurality of desired metered flow rates for a given syringe discharge pressure and fluid viscosity, and connecting fittings formed on opposite ends of each of said tube connecting sets to enable connection of any selected one of said assortment of tube connecting sets between said syringe body discharge opening and a patient to whom delivery of fluid is desired to be effected, the respective said flexible tubing section of each of said plurality of tube connecting sets having a length relative to the combination of its bore size, the viscosity of fluid desired to be delivered therethrough, and the fluid discharge pressure exerted at said syringe body discharge opening during effective fluid-discharge-effecting application of said constant force driver means to said syringe, which according to Poiseuille's Law will effect a single selected flow rate through the respective said flexible tubing section, whereby a health professional may select and use from said assortment any one of said plurality of tube connecting sets from said assortment for connection between said syringe and a patient to effect the corresponding predetermined fixed flow rate of delivery of a said desired fluid to a patient, the tubing section of each of said tube connecting sets of said assortment including an outer circumferential overcoat layer of plastic formed over an inner tubing section, said assortment including a plurality of tube connecting sets whose respective said inner tubing sections are of different outer diameter as well as different inner diameter, said outer overcoat layer for all of said tube connector sets being of substantially the same outer peripheral size along its length, independent of the inner bore size and/or outer peripheral size of the various respective inner tubing sections of such tube connector sets, to thereby accommodate and accept end connecting fittings of a tube connecting bore size common to all of said tube connecting sets independent of the inner bore size and flow rate of any given tube connecting set of said assortment.
 2. An arrangement according to claim 1,said inner flexible tubing section being formed of plastic tubing.
 3. An arrangement according to claim 1,said inner flexible tubing section being formed of thin-walled glass tubing.
 4. An arrangement according to claim 1,said inner flexible tubing section being formed of metal.
 5. An arrangement according to claim 1,each of said tube connecting sets having identifying indicia in association therewith to enable determination by a health professional of its respective fixed metered flow rate rating of said given syringe discharge pressure and fluid viscosity.
 6. An arrangement according to claim 5,said indicia being formed on the respective said outer overcoat layer of each respective said tube connecting set.
 7. An arrangement according to claim 5,said indicia being a respective color indicia for each respective flow rate rating.
 8. A kit assortment of tube connecting sets for selective connection of a substantially constant-force-driven syringe to a patient for delivery of fluid thereto from said syringe body, each of which tube connecting sets has the additional dual function of forming a fixed flow rate fluid metering means,each of said tube connecting sets of said assortment being formed of a flexible tubing section having a bore of substantially constant cross-section size along its length which bore is very small compared to its length and which taken over its entire length forms a substantial and effective predetermined flow-rate-restrictive metering means for administering medical fluids therethrough, and said bore being further substantially larger in cross-section than any particle which might occur in a medical fluid to be delivered therethrough, so as to enable said tubing section to form a predetermined fixed flow rate fluid metering means which is fully operational without need for a filter, said kit assortment of tube connecting sets including a plurality of tube connecting sets each of which itself forms a combined flexible tube connecting set and predetermined fixed flow rate metering means and provides a different one of a plurality of desired metered flow rates for a given syringe discharge pressure and fluid viscosity, and end connecting fittings formed on opposite ends of each of said tube connecting sets to enable connection of any selected one of said assortment of tube connecting sets between a syringe and a patient to whom delivery of fluid is desired to be effected, the respective said flexible tubing section of each of said plurality of tube connecting sets having a length relative to the combination of its bore size, the viscosity of fluid desired to be delivered therethrough, and the fluid discharge pressure exerted by a constant-force-driven syringe to which a selected one of said tube connecting sets is to be connected, which according to Poiseuille's Law will effect a single selected flow rate through the respective said flexible tubing section, whereby a health professional may select and use from said assortment any one of said plurality of tube connecting sets from said assortment for connection between a said substantially constant-force-driven syringe and a patient to effect the corresponding predetermined fixed flow rate of delivery of a said selected one of said plurality of tube connecting sets from said assortment, the flexible tubing section of each of said tube connecting sets of said assortment including an outer overcoat layer of plastic formed over an inner flexible tubing section, said outer overcoat layer for all of said tube connector sets being of effectively substantially the same outer peripheral size along its length, independent of the inner and/or outer peripheral size of the various inner flexible plastic tubing of such tube connector sets.
 9. An arrangement according to claim 8,said inner flexible tubing section being formed of plastic tubing.
 10. An arrangement according to claim 8,said inner flexible tubing section being formed of thin-walled glass tubing.
 11. An arrangement according to claim 8,said inner flexible tubing section being formed of metal.
 12. An arrangement according to claim 8,each of said tube connecting sets having identifying indicia in association therewith to enable determination by a health professional of its respective fixed metered flow rate rating for said given syringe discharge pressure and fluid viscosity.
 13. An arrangement according to claim 12,said indicia being formed on the respective said outer overcoat layer of each respective said tube connecting set.
 14. An arrangement according to claim 12,said indicia being a respective distinctive color indicia indicative of each respective flow rate rating. 